<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>在下拉列表中选择多个选项</title>
</head>

<body>

</body>
<form>
    <select id="mySelect" size="4">
        <option>苹果</option>
        <option>梨子</option>
        <option>香蕉</option>
        <option>橙子</option>
    </select>
    <input type="button" onclick="selectMultiple()" value="选择多个">
</form>

</html>
<p>在你点击“选择多个”按钮之前,尽量选择一个以上的选项(通过按下shift或Ctrl键)。然后尝试点击“选择多个”按钮。</p>